Electromagnetic switching device with restricted guidance

ABSTRACT

An electromagnetic switching device (2) with restricted guidance, in which the closure contacts do not come into contact when the break contact is welded or fixed. An elastically resilient transmission lever (10) is provided to establish the effective connection between the armature (8) and the contact support (12) extending at a distance from and parallel to the armature.

FIELD OF THE INVENTION

The present invention relates to an electromagnetic switchgear withrestricted guidance in which the make contacts do not touch while thebreak contact is fixed.

RELATED TECHNOLOGY

This kind of electromagnetic switchgear, disclosed in German PatentApplication No. 35 40 460 A1, contains a magnet system, which containsan armature; a movable contact carrier, which with fixed contacts holdmovable contact parts forming break and make contacts and which assumesa rest position effected by spring force; and an additional elasticconnection between the armature and the contact carrier in the form of aspring supported against the armature by a clip, by which it becomespossible with a welded break contact to move the armature withoutactivating the make contacts (restricted guidance). An electromagneticswitchgear according to European Patent No. 358 050 B1 is furtherdeveloped in such a way that, with a welded break contact, the magnetsystem yoke, which is elastically supported against the switchgearcasing, can approach until the magnet system is closed. The disadvantageof the current state of technology is that additional elastic parts areneeded to achieve the restricted guidance. It is not clear from thecurrent state of technology how restricted guidance should be realizedfor electromagnetic switchgears in which the armature and contactcarrier are arranged in parallel planes and whose movement directionsthus run not behind one another but parallel or antiparallel, as isoften the case with small contactors. (See for example German Patent No.31 46 780 C2.

SUMMARY OF THE INVENTION

An object of the present invention is to achieve the restricted guidancewithout additional component parts and for the case of parallelarrangement of the armature and contact carrier.

The present invention provides that the movements of armature andcontact carrier take place in parallel with a gap and provides anelastically flexible transmission lever which establishes the operativeconnection between the armature and contact carrier. In this way,without additional component parts, it is achieved that, when breakcontacts are fixed as a result of welding or mechanical barring,movement of the armature is permitted without activating a make contact.

In an advantageous further development, the support of the transmissionlever against the switchgear casing favorably affects the transmissionratio of the forces to be transmitted. This is especially so when thetransmission lever is coupled at one free end with the armature, issupported with the other free end against the casing part that holds thecontact carrier, and is coupled with the contact carrier between bothends.

In another advantageous further development of the present invention,the use of a transmission lever with a maximum transmission force,particularly through spring elasticity, provides a secure closing of themagnet system, although the contact carrier cannot be moved as a resultof a fixed break contact. Such spring-like flexible transmissionelements are known per se as snap elements in other contexts, forexample according to German Patent Application No. 39 27 219 A1.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be explained in greater detail below using anexemplary embodiment from which further details and advantages can beseen. In the corresponding drawing,

FIG. 1 shows an electromagnetic switchgear according to the presentinvention schematically depicted in the off position;

FIG. 2 shows the same in the on position

FIG. 3 shows the same in the blocked on position.

DETAILED DESCRIPTION

In FIG. 1 and FIG. 2, electromagnetic switchgear 2 is surrounded by aswitchgear casing 4. Within switchgear casing 4 a magnet system isarranged as a contact drive, which includes a fixed magnet part 6 and amovable armature 8. The linear movement of armature 8 toward fixedmagnet part 6, caused when the magnet system is activated, istransmitted by a transmission lever 10 to a contact bridge 12 which ismovable in parallel to armature 8. Movable contact parts, which are notdepicted, are held on contact carrier 12, and they form break or makecontacts with fixed contacts attached to switchgear casing 4. In the offposition as shown in FIG. 1, the break contacts are closed and the makecontacts open, while restoring spring forces, which are not depicted indetail, impact on armature 8 and/or contact carrier 12. In the onposition as shown in FIG. 2, the break contacts are open and the makecontacts are closed. The transmission lever 10 is coupled at its freeend 14 with armature 8. It is supported at its other free end 16 againsta support position 18 located on that casing part of switchgear casing 4in which the contact carrier 12 is placed. Between its two ends 14 and16, the transmission lever is coupled with contact carrier 12, so thatwhen the magnet system is deactivated or activated the movement ofarmature 8 occurs, with a favorable force transmission ratio into thecorresponding parallel movement of the contact carrier into the offposition (FIG. 1) or into the on position (FIG. 2).

FIG. 3 depicts the case when at least one break contact is welded orcontact carrier 12 is blocked by a mechanical barring device notdepicted. In this way, when the magnet system is activated, acounterforce F is applied to contact carrier 12. Normally, armature 8could no longer move toward fixed magnet part 6. This would result in anoverloading of the magnet system, in particular to burn-out of itsexciting winding, which is not depicted, or to a bending of breakcontacts and, as a result, to the closing of the make contacts. It isadvantageous for transmission lever 10 to be designed as an elasticallyflexible lever (snap lever), which yields in a spring-like manner when acritical stress is exceeded. In this way, on the one hand, the magnetsystem is closed by magnetic contacting of armature 8 with fixed magnetpart 6, and on the other hand counterforce F on contact carrier 12 islimited. This effectively prevents both the overloading of the magnetcircuit and the closing of the make contact, that is, the restrictedguidance of the electromagnetic switchgear is guaranteed in all cases.The term parallel movement as used herein includes parallel oranti-parallel movement.

What is claimed is:
 1. An electromagnetic switchgear with restrictedguidance comprising;a magnetic system having an armature movable alongan armature movement path; a movable contact carrier holding movablecontact parts forming a break contact and a make contact with fixedcontacts, the movable contact carrier having a rest position effected bya spring force and being movable parallel to the armature movement path,the movable contact carrier being spaced by a gap from the armaturemovement path; and an elastically flexible transmission leveroperatively connecting the armature and the contact carrier, thearmature and the contact carrier being elastically connected so that thearmature moves without activating the make contact when the breakcontact is welded or blocked.
 2. The electromagnetic switchgear asrecited in claim 1 wherein when the break contact is welded or blockedthe break contact is capable of providing a counterforce on the contactcarrier, the counterforce being limited as a function of a maximumtransmission force of the flexible transmission lever on the contactcarrier.
 3. The electromagnetic switchgear as recited in claim 2 whereinthe transmission lever has a spring characteristic so that thetransmission lever yields when the counterforce exceeds a certain level.4. The electromagnetic switchgear as recited in claim 1 wherein thetransmission lever is supported against a switchgear casing.
 5. Theelectromagnetic switchgear as recited in claim 4 wherein when the breakcontact is welded or blocked the break contact is capable of providing acounterforce on the contact carrier, the counterforce being limited as afunction of a maximum transmission force of the flexible transmissionlever on the contact carrier.
 6. The electromagnetic switchgear asrecited in claim 5 wherein the transmission lever has a springcharacteristic so that the transmission lever yields when thecounterforce exceeds a certain level.
 7. An electromagnetic switchgearwith restricted guidance comprising:a magnetic system having an armaturemovable along an armature movement path; a movable contact carrier forholding movable contact parts forming a break contact and a make contactwith fixed contacts, the movable contact carrier having a rest positioneffected by a spring force and being movable parallel to the armaturemovement path, the movable contact carrier being spaced by a gap fromthe armature movement path; and an elastically flexible transmissionlever operatively connecting the armature and the contact carrier, thearmature and the contact carrier being elastically connected so that thearmature is capable of moving without activating the make contact whenthe break contact is welded or blocked; the transmission lever beingcoupled at one free end with the armature, supported at an other freeend against a part of the switchgear casing holding the contact carrier,and coupled with the contact carrier between the one free end and theother free end.
 8. An electromagnetic switchgear with restrictedguidance comprising:a magnetic system having an armature movable alongan armature movement path; a movable contact carrier for holding movablecontact parts forming a break contact and a make contact with fixedcontacts, the movable contact carrier having a rest position effected bya spring force and being movable parallel to the armature movement path,the movable contact carrier being spaced by a gap from the armaturemovement path; and an elastically flexible transmission leveroperatively connecting the armature and the contact carrier, thearmature and the contact carrier being elastically connected so that thearmature is capable of moving without activating the make contact whenthe break contact is welded or blocked; wherein when the break contactis welded or blocked the break contact is capable of providing acounterforce on the contact carrier, the counterforce being limited as afunction of a maximum transmission force of the flexible transmissionlever on the contact carrier; the transmission lever being coupled atone free end with the armature, supported at an other free end against apart of the switchgear casing holding the contact carrier, and coupledwith the contact carrier between the one free end and the other freeend.
 9. The electromagnetic switchgear as recited in claim 8 wherein thetransmission lever has a spring characteristic so that the transmissionlever yields when the counterforce exceeds a certain level.